Cleaner for tin, zinc, and aluminum



Patented Apr. 14, 1936 srrss CLEANER FOR TIN, ZINC, AND ALUMINUM Charles B. Durgin, Annistom, Ala.I assignor to Swann Research, Incorporated, a corporation of Alabama No Drawing. Application November 23, 1932, Serial No. 644,080

1 Claim.

This invention relates to a cleaner or alkaline detergent for general cleaning purposes, and especially for cleaning those metal surfaces which are commonly etched or discolored by the action 5 of the ordinary alkaline detergents.

Dairy equipment, such as containers, coolers and the like which are ordinarily constructed of sheet iron or other metal coated with a heavy bright deposit of tin, is largely used but is diflicult to keep clean because of the formation of greasy deposits such as milk stone and the like upon the surfaces exposed to milk. Furthermore, aluminum is largely used for cooking utensils, while zinc is used to an appreciable extent for miscellaneous protective purposes in the home.

While many alkaline detergents have been proposed for cleaning metal surfaces, it is a matter of common knowledge that the metals tin, aluminum and zinc as well as others are rather easily discolored or etched by the common alkaline detergents. Such alkaline detergents as are now in use are effective in removal of dirt and grease, but because of the above-mentioned unsightly discoloration formed on the surfaces, it is in many cases necessary to apply a mild abrasive to the surfaces to remove the discoloration and restore the bright luster of the metal. The use of such an abrasive is generally expensive and unsatisfactory and often causes premature failure of the surface coating or even of the article itself.

Accordingly a general-purpose composite alkaline cleaner was much to be desired.

It is accordingly a prime object of this invention to provide a cleaner which can be used generally on the surfaces of metals commonly attacked by the known alkaline detergents, and especially on surfaces of tin, aluminum" and zinc,

and which may be composed of one or more,

of the known alkaline detergents in combination with an agent adapted to effectively minimize the formation thereon of unsightly discolorations or stains.

A further object is the provision of a method by which those metallic surfaces which are readily discolored by alkaline detergents may be cleaned without discoloration or etching by a simple washing process and without the use of a subsequent polishing operation.

der or similar materials. In many cases mixtures of the above-mentioned materials are employed,

Those alkaline detergents which I embrace and I contemplate as one feature of my invention such a mixture of two or more of the abovementioned ingredients, to which other materials may also be added if desired, as will hereafter be more fully set out. 5 I In conducting experiments to overcome the discoloration of surfaces of metals, such as those mentioned, by alkaline cleaners, I discovered that a combinationof such alkaline cleaner with an alkali metal perborate, say sodium perborate, 10

while not itself satisfactory for the prevention of discoloration of metal surfaces during long exposure, could readily be rendered suitable by the addition to such combination of a second body which appeared to exert, over much longer periods 15 of time, a protective action on the metal surfaces upon which the composite cleaner was used, so that such discoloration or etching was effectively minimized. Such second body-is ordinarily effective in the prevention or inhibition of dis- 2 coloration only when used in the presence, both of the alkaline detergents and the alkali metal perborate, when this composite cleaner is used in water solution, as is customarily the practice. The second body which I have found to be effective in inhibiting the discoloration or corrosion of metal, especially tin surfaces, may be either an alkaline earth metal salt or an alkali metal "silicate, or preferably a combination of both. Such soluble alkaline earth metal salts as magnesium sulphate, cadmium sulphate, zinc sulphate, calcium chloride, barium chloride or sodium silicate may be employed in compounding my composite cleanser. Those corrosion inhibitors which I have found satisfactory may for the present invention be classified in the second group of the periodic table, especially in the second to fifth inclusive periods of such table. In the production of ,a composite cleaner for metal, f especially tin surfaces, I prefer to use one or more 40 of the above-mentioned corrosion inhibitors and especially prefer to employ in combination magnesium sulphate and a sodium silicate, particularly one in which the ratio of Nazi) to $10: is in the neighborhood'of 1:2 to 1:32, and which is water-soluble, altho it may be diflicultly soluble.

Several specific examples will serve to further illustrate my invention. I v

Example I Mix together trisodium phosphate crystalline 88 parts, sodium perborate 10 parts and magnesi um sulphate 2 parts. These three ingredients are incorporated together in the dry state, and if desired, other proportions than those herein spe- 'point of the solution.

Example II I may also employ as the base of my improved cleaner a sodium metasilicate such as is now on the market, or I may even employ a still more alkaline silicate than the metasilicate, say a sodium orthosilicate or even a mixture of the meta and the orthosilicates. The preferred composition, when employing a sodium metasilicate, may be as follows:-

Parts by weight Sodium metasilicate 88 Sodium perborate 10 Magnesium sulphate or other soluble magnesium salt 2 The relative proportions may, of course, be varied from the above specific limits, which are given by way of illustration only. The composite cleanser may be used in much the same way as described in Example I.

Example III A composite cleaner suitable for tin, zinc and aluminum, according to a preferred form of my invention, may be illustrated by the following specific proportions:

Parts Sodium silicate in which the NaaO:SiOz ratio is 1:2 to 1: g 25 Trisodium phosphate crystalline 63 Sodium perborate 10 Magnesium sulphate 2 The composite cleanser is compounded by mixing the dry materials above-mentioned and may be used on tin, aluminum and zinc in the manner above described. Other proportions'may be employed, if desired. In the above formula I may,

if desired, substitute the trisodium phosphate completely or only partly with the sodium metasilicate.

In the above-mentioned detergent compositions it will be noted that two forms of sodium silicate are employed, one being a low alkali ratio silicate, the ratio of NazO to SiOz being 1:2 to 1:32; the other being metasilicate in which the Nazozsioz ratio is 1:1 or even 2: 1 (orthosilicate) The low alkali ratio silicate is preferably not employed together in compositions with the higher ratio silicate, altho it may be. The function of the low alkali ratio silicate, which is not a detergent in the present invention, is'to enhance the efiectiveness of the soluble magnesium or other alkaline earth salt in inhibiting discoloration or etching of the metal surfaces, for which purpose it is particularly eifective. In those compositions in which the high alkali ratio silicates are employed, they are therein employed in relatively large proportion, since these high ratio silicates function strictly as detergents.

While I have given specific proportions in which the various ingredients of my composite detergent may be compounded, it will be appreciated that such specific proportions are given by way of illustration only, and are not to be construed as limitations. It may be said, however, that in the preferred form of my composition the proportion of the alkaline detergent will be at least equal to or greater than all the other. constituents therein contained. The proportion of perborate will usually be a minor part of the total (5 to 20%); the proportion of the low alkali ratio silicate, if used, will be equal to or even 2 to 2.5 times as great as the proportion of the perborate; while the proportion of soluble magnesium or other alkaline earth metal salt will be from one-fifth to one-half of the perborate in amount.

While I have described herein only three embodiments of my invention, it will be apparent that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire that only such limitations be placed thereupon as may be imposed by the prior art or as is specifically set forth in the appended claim.

WhatI claim is:--

A cleaner for tin, zinc and aluminum surfaces comprising the following ingredients in approximately the proportions givem- Parts Trisodium phosphate 63 Sodium perborate 10 Sodium silicate in which the NazOzSiOa ratio is 1:2 to 1: 2 Magnesium sulphate 2 CHARLES B. DU'RGIN. 

